1. Field of the Invention
The present invention relates to a light guide plate mold core for making a light guide plate used in a liquid crystal display, and a method for manufacturing the light guide plate mold core.
2. Description of the Prior Art
A common type of liquid crystal panel needs a backlight module to provide uniform light and clear viewing of displayed images. A backlight module usually comprises a light source, a light guide plate, and a reflective plate. Light emitted from the light source is directed into the light guide plate, and the light guide plate and the reflective plate guide the light to emit from an emitting surface of the light guide plate. Then the light enters a diffuser, and the diffuser diffuses the light to provide uniform luminance for the liquid crystal panel. Usually, in order to attain uniform emitting light, some special optical structures are disposed on a bottom surface of the light guide plate to disperse light that would otherwise be singly internally reflected. The bottom surface is opposite to the emitting surface, and the optical structures typically are scattering dots.
Nowadays, methods for manufacturing a light guide plate are classified into two types: printing methods and non-printing methods. The printing method typically includes the following steps: printing some printing materials on a bottom surface of a light guide plate substrate, the printing materials being doped with highly diffusive materials such as silicon dioxide (SiO2) and titanium oxide (TiO2); and heating and curing the printed materials. The diffusing materials are used to disperse what would otherwise be single internal reflections of incident light in the light guide plate. That is, the diffusing materials help scatter light before it is transmitted from the emitting surface, thereby providing uniform luminance for a liquid crystal panel.
The non-printing method typically includes the following steps: forming specific patterns on a surface of a light guide plate mold; injecting molten Polymethyl Methacrylate (PMMA) into the mold; and cooling the mold to obtain a light guide plate having corresponding desired specific patterns. The patterns are formed without any heating of a preform of the light guide plate. Thus the non-printing method has the benefit of lower costs.
A light guide plate mold core used in the light guide plate mold has two main functions: forming patterns on the light guide plate so that the light guide plate can attain uniform emitting light from light input from the light source, and controlling the speed of cooling of the molten Polymethyl Methacrylate. Conventional mold cores are made of stainless steel, and the speed of cooling of the molten Polymethyl Methacrylate is so fast that stresses within the formed light guide plate cannot be entirely released. That is, the surface of the light guide plate is liable to be uneven or bent. This reduces the uniformity of reflection and transmission of light within and from the light guide plate. The optical characteristics of the backlight module and thus the liquid crystal display are detrimentally affected.